This invention relates to laser apparatus, and more particularly to laser apparatus of the type which can successively sweep the frequency of the laser's output beam over a wide range.
There is frequently a requirement in optical communications, measurement and other fields for a laser apparatus the output beam of which can be swept in frequency over a wide range. A known laser apparatus which can sweep the frequency of its output beam comprises a laser device such as a semiconductor, dye, or solid state laser and a pair of optical resonators having wavelength selectivity. The frequency of such a laser apparatus is swept by successively changing the angle of the optical resonators. Another type of known laser apparatus has a non-linear crystal. The frequency of this apparatus then may be swept by changing the temperature of the non-linear crystal. These known laser apparatuses, however, are bulky and cannot sweep the frequency quickly enough.
Semiconductor lasers which can rapidly sweep their frequency bands are known. Such a laser is described in a paper entitled "Integrated Electro-Optic Intracavity Frequency Modulation of Double-Heterostructure Injection Laser" by F. K. Reinhart et al, Applied Physics Letter, Vol. 27, No. 10, Nov. 15, 1975. However, this type of laser apparatus is limited in the range of frequencies over which it can sweep.